Coatings for masonry substrates and the like typically require resin binders with good elongation characteristics. Water based coating compositions with resin binders derived from carboxylic acid functional monomers are often used. Zinc oxide is widely used as a coating additive, especially for exterior coating applications. A problem with using zinc oxide in water based coating compositions of this type is that the zinc oxide generates zinc ions which often form complexes with the carboxylic acid groups. This tends to reduce the elasticity of the coating. This invention provides a solution to this problem.